Technical Field

The invention relates to bleaching of all dyed textile products such as yarns, fabrics, and garments.

The invention specifically relates to a composition regarding the oxidation and/or bleaching of the all textile products such as yarns, fabrics, and garments dyed with indigo dyes, sulfur dyes or oxidized dyes and to a method using this composition. The novel bleaching composition comprises various cyclic anhydride derivatives and an aqueous hydrogen peroxide solution which is activated by phosphate salts.

Prior Art

All textile products and especially denim garments such as jeans, jackets and skirts dyed especially with indigo or other dyes are considered as the most attractive fashion trend by many, when they have a “wash-out” or“worn-look” appearance. For this reason, the trend of “used” or“vintage look” appearance has become one of the most important fashion types in the fashion sector.

Amongst the various denim finishing methods including stone washing, ice washing, mechanical abrasion during laundering or sand blasting to produce a particular appearance, the most common type of finishing method is the oxidation-based chemical bleaching methods contributing oxygen to the dye (usually indigo alone or in combination with sulfur black) which would result in permanent whiteness on the corresponding exposed parts. The degree of bleaching action depends on the strength of the bleaching agent, temperature and duration of the treatment.

Along the years, many bleaching compositions regarding lighten the local areas or the whole surface of the dyed textile products included sodium hypochlorite as a bleaching material, which is cost efficient and yielding, which can be obtained existing for many numbers of oxidizable dyes, including the indigo and the indigoid dyes. However; this chlorine based procedure produces a great amount of wastewater which is contaminated with absorbable organic halogens (AOX) and in addition, the waste waters that are generated as a result of the process usually require extra chemical process in order to fulfill the standard limitations decided by the environmental organizations.

The use of potassium permanganate with the purpose of local bleaching the indigo dyed denim garments by a spraying method is a remarkable general process due to the fact that it is reliable and durable. It is an effective procedure, but it also has serious disadvantages due to the fact that potassium permanganate belongs to the toxic substance class in high temperatures. It possesses serious dangers to the environment and to health and its massive use results in high levels of heavy metal contamination in the water and consequently requires extra steps of manganese oxide and unconsumed permanganate. The use of potassium permanganate is restricted with strict regulations. In many countries, a requirement of providing evidence exists in order to prevent the misuse of the potassium permanganate.

National patent application with number TR 2012/07923 is related to obtaining a pattern, shape, letter, picture effect by removing the dye layer on the textile product and by performing bleaching by spraying the sodium bicarbonate solution in a regular or irregular manner. This method requires the removal of the dye layer and therefore; it is not seen as an efficient bleaching method in the industry. On the other hand, in the national patent application with number TR 2012/07923, a method of obtaining the sodium hypochlorite from the sea water, lake water, rock salt or sea water is described. It is stated that the hypochlorite obtained this manner can be used as a laundry bleaching agent for the purpose of cleaning. As it is stated above; the usage of hypochlorite as an industrial bleaching agent creates an environmental contamination, which is irreversible.

Studies with the aim of providing an alternative to the hypochlorite and the potassium permanganate and developing novel solutions have been frequent in the recent years. Despite this, a few approaches with the potential of providing limited improvement have been found to have disadvantages and a practical use in comparison with the permanganate process has not been found. With this aim, among the other patents, the patents with numbers US5749923A and EP0654557A describe that the bleaching method which is based on the removal of the indigo dye from the fibers can be performed by turning the indigo dye into the water soluble leuco form by using a combination of the reductive agents such as the formamidine sulfinic acid and some carbon hydride derivatives. However, this bleaching process shall be performed in a high temperature (> 80 ° C) and a high alkali medium (pH> 11 ); in addition the medium shall be oxygen-free; in the contrary case; the leuco form which is produced locally can be re-oxidized with the atmospheric oxygen in a rapid manner.

Patent documents with numbers US 20173384596C, US 20174443352C, EP 0027693 a and DE 3400950A explain the use of monoperoxophthalic acid and water soluble salts with some alkali salts as bleaching agent. However; the stability of the peroxocarboxylic acids is very limited and they cannot provide sufficient performance and a constant activity in the mass production processes, which require long durations of time.

The bleaching effect can be obtained with a greatly reduced environmental impact (EP 0554648A), without using the chemicals, by applying ozone as an oxidant to the dyed cotton fabrics. In addition to this, ozone is a very powerful oxidizing agent which can be used to enable the denim garments being completely bleached in a closed system; thus; local treatments are not possible. In practice, the production and control of the ozone play essential role in process, requiring complicated systems and automated safety devices.

As an alternative, the hydrogen peroxide has become the most sustainable oxidizing agent because it is not harmful to the environment and it can be slowly dissolved into water and oxygen in nature. In addition to that, the hydrogen peroxide does not create a problem of wastewater which is related with the chlorine based bleaching. In the meantime, it is known that simple hydrogen peroxide solutions are not efficient in bleaching without additive agent. USA patents numbered 4363699, 5482516, 4496472 and 4337060, disclose that the alkali solution of hydrogen peroxide produces too fast a rate of decomposition. Thus, a suitable stabilizer such as alpha-hydroxyacrylic acid polymer, oligomer of phosphonic acid ester and potassium orthosilicate have to be used in order to control the rate of decomposition of the hydrogen peroxide. This process is not a very efficient method due to the problems that can be caused by the added stabilizers and a long period of time is needed for obtaining the whiteness values that are acceptable.

Considering the disadvantages of the processes stated above, it can be easily understood that why potassium permanganate is the most preferred method in bleaching processes. As a result, in order to avoid the disadvantages of the bleaching methods in the prior art and in order to bleach all textile products dyed with oxidizable dyes, including indigo dyed or Sulphur dyed denim garments, without permanganate and chlorine; a novel method is needed.

Brief Description of the Invention

The present invention is related to a bleaching composition for dyed textile products, which fulfills all the needs mentioned above, which eliminated all the disadvantages and provides some additional advantages and to a bleaching method which uses this composition.

The primary object of the invention is to provide a composition regarding the oxidation and/or bleaching of the all textile products including oxidizable dyes and coloring agents such as yarns, fabrics, and garments; especially including indigo dyed and/or Sulphur dyed denim textile products and a method using this composition and textile products manufactured in this way.

Another object of the invention is to provide a method which avoids all the disadvantages of the bleaching methods in the prior art and which enables bleaching of the indigo dyed or Sulphur dyed denim textile products without using permanganate and chlorine.

Another object of the invention is to provide an improved bleaching method which eliminates potential disadvantages and hazards for the environment by using hydrogen peroxide as the main component in the bleaching composition.

Another object of the invention is to provide a bleaching method which enables the production of fashion garments wash-out or worn-look appearance without a serious degradation of the denim textile products and without use of strong chemical bleaching agents.

Another object of the present invention is to provide a new environmentally friendly and cost effective composition and bleaching method which minimizes environmental impact, provides rapid bleaching process, since the neutralization step is not required after bleaching application.

In order for the objects that are mentioned above to be realized, the present invention is a bleaching composition for oxidation and/or bleaching of dyed textile products, comprising • at least one cyclic anhydride,

• a hydrogen peroxide aqueous solution which comprises excess hydrogen peroxide in a manner to have at least 20 times greater equivalent molar ratio in comparison to the cyclic anhydride,

• at least one phosphate based alkali salt which increases the solubility of the cyclic anhydride in the hydrogen peroxide aqueous solution and adjusting the pH of the acidic solution; and maintaining active content of in situ prepared solution up to 48 hours, thanks to the conversion of the carboxylic acids, which are formed by decomposition of active bleaching ingredient peroxycarboxylic acids those formed by reaction of cyclic anhydride with hydrogen peroxide; to the peroxycarboxylic acids in presence of excess hydrogen peroxide; and not requireing a neutralization after the application.

In order for the aims mentioned above to be realized; the present invention is a method of oxidation and/or bleaching of dyed textile products; characterized by comprising treatment of the textile product with in situ prepared active solution without requiring a neutralization after treatment, wherein the solution is prepared in acidic pH conditions with at least one cyclic anhydride and a hydrogen peroxide aqueous solution which includes excess hydrogen peroxide in a manner to have at least 20 times greater equivalent molar ratio in comparison to the said cyclic anhydride and at least one phosphate based alkali salt.

The structural and characteristic features and all of the advantages of the present invention will be understood better by the detailed description disclosed below and therefore; an evaluation shall be made by taking this detailed description into the account.

Detailed Description of the Invention

In this detailed description, a bleaching composition of the invention, which is used for the textile products, a method using this composition and the preferred applications are explained for the mere purpose for the issue to be understood better and this description is not limiting in any manner. The invention is based on the principle that some cyclic anhydride derivatives; especially phthalic anhydride, glutaric anhydride, maleic anhydride, succinic anhydride, cyclohexane-1 ,2-dicarboxylic anhydride, pyromellitic dianhydride, ethylenediaminetetraacetic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-Oxydiphthalic anhydride and benzophenone-3,3',4,4'-tetracarboxylic dianhydride which include aliphatic or aromatic hydrophobic side groups, have a reaction with the excess amount of the hydrogen peroxide aqueous solution, in order to produce the peroxycarboxylic acids.

In the studies performed by the inventors of the present invention, it is found that the use of excess hydrogen peroxide in a manner to have minimum 20 times greater equivalent molar ratio in comparison to the cyclic anhydride accelerate the reaction via entropic effect and surprisingly stabilizes the occurring of peroxycarboxylic acids. In the bleaching composition of the invention generated this way; peroxycarboxylic acids decompose by time in aqueous solution and generate carboxylic acids; however, the occurred carboxylic acids form peroxycarboxylic acids again successively with the excess hydrogen peroxide presence in the hydrogen peroxide aqueous solution. The schema of the balanced reaction which occurs here is shown below.

Active bleaching solution

(I) cyclic anhydride

(II) peroxycarboxylic acid

(III) carboxylic acid As it can be seen in the schema shown above; in the bleaching composition of the invention; peroxycarboxylic acids are generated as a result of the reaction of the cyclic anhydrides with the hydrogen peroxide aqueous solution, which includes at least 20 times more hydrogen peroxide as equivalent molar ratio in comparison to the cyclic anhydride; the generated peroxycarboxylic acids decompose in the aqueous medium and create carboxylic acids; the generated carboxylic acids reacts with the excess hydrogen peroxide in the solution again and create peroxycarboxylic acids again. By the virtue of this stabilization strategy, depending on the type and ratio of the used cyclic anhydride; the bleaching composition of the invention maintains its active content in the same concentration up to 48 hours after the active aqueous solution is prepared. Keeping the reactivity of bleaching solution in the same level is the main distinctive feature of this invention, making the important contribution to the sustainability of consistent bleaching effect for every product in the mass denim production processes in textile manufacturing establishments. In the bleaching composition of the invention, after the preparation of the active aqueous solution, the bleaching effect is obtained by the peroxycarboxylic acids and at the same time, the excess hydrogen peroxide in the solution also contributes to the bleaching effect.

Cyclic anhydrites are preferred in the bleaching composition of the invention because due to the ring strain, the cyclic anhydrides are more prone to give ring opening reaction via nucleophilic attack of hydrogen peroxide to form peroxycarboxylic acids. However, aliphatic and aromatic pendant groups which are intentionally preferred for this process and mostly keeping active substances on the surface of garment due to their hydrophobicity and are also decreasing the solubility in an aqueous environment. For this reason, in the bleaching composition of the invention; phosphate based alkali salts; especially disodium hydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen, sodium tripolyphosphate, potassium tripolyphosphate, trisodium phosphate, tripotassium phosphate are used successfully as an additive agent in order to increase the solubility of the anhydride in the hydrogen peroxide aqueous solution. The said phosphate salts not only increase the solubility of the anhydrites but also adjust the pH of the active solution having strong acidic structure, and therefore prevents degradation of bleached textile product. Since the peroxycarboxylic acids have the highest bleaching efficiency in the acidic media; the pH of the bleaching composition of the invention is optimized by being set to the range of pH 1 to pH 6; more preferably to the range of pH 1.5 to pH 4.0. By means of the present invention; every kind of textile products such as yarns, fabrics or garments which are dyed with the oxidizable dyes, can be bleached without needing a neutralization process by treating with the activate bleaching solution comprising of hydrogen peroxide, cyclic anhydride derivatives and phosphate salts. The regenerated yarns which inert during the textile manufacturing can be bleached and reused. Bleaching can be performed on the fabric or garments to provide wash-out or worn-look appearance. The invention is especially suitable for bleaching of the textile products, which are dyed with indigo dyes, indigoid dyes or Sulphur black or a combination thereof, by using local spraying, fog or other methods and without needing a neutralization step. The active bleaching solution can provide a bleaching effect at room temperature for indigo dyed light colored denim garments or sulphur dyed dark colored denim garments. By using the active bleaching composition of the invention, every kind of textile which are dyed with oxidizable dyes can be bleached at a medium temperature between 20 to 80°C. The invention provides a method which is environment friendly in the sense that it eliminates the need of the neutralization in the bleaching process and which is suitable for mass production due to its stable structure.

In the studies performed in the scope of the invention, the effect of an active bleaching solution on a bleaching process is tested by measuring the alteration of coloring power in the unprocessed denim textiles and in the processed denim textiles.

The bleaching effect was determined on indigo-dyed and sulphur-dyed two different denim fabrics having same mechanical properties, each with determining the color strength according to the CIE with X-Rite Ci7860 spectrophotometer calibrated by standard light D 65.

For each test, approximately 1.5 gr of active bleaching solution are sprayed onto the denim surface of the same size and kept in a tumbler at 80°C for 10 minutes, afterwards a cold rinsing is performed without any neutralization and the denims are dried in a tumbler. The color strength was calculated as percentage, measured according to CIE comparing the changes in color strength of untreated reference denim fabric and treated denim fabric. For the reference untreated denims, the color strength was accepted as 100%. Example 1

Phthalic anhydride (1 mol) was mixed with aqueous hydrogen peroxide (50% w/w) (22 mol) at 40°C and adjusted to a pH of 2.0 - 2.5 with phosphate salts. Of this solution, 1.5 g of active bleaching solution was applied on same type and size of two different denim fabrics dyed with indigo (Denim 1 ) and sulphur black (Denim 2), then, kept in tumbler at 80 °C for 10 min. After that, the samples were rinsed with cold water without neutralization, followed by drying in a tumbler. The change in color strength is 60% for Denim 1 , 40% for Denim 2.

Example 2

Succinic anhydride (1 mol) was mixed with aqueous hydrogen peroxide (50% w/w) (22 mol) at 40°C and adjusted to a pH of 2.0 - 2.5 with phosphate salts. Of this solution, 1.5 g of active bleaching solution was applied on same type and size of two different denim fabrics dyed with indigo (Denim 1 ) and sulphur black (Denim 2), then, kept in tumbler at 80 °C for 10 min. After that, the samples were rinsed with cold water without neutralization, followed by drying in a tumbler. The change in color strength is 65% for Denim 1 , 55% for Denim 2.

Example 3

Maleic anhydride (1 mol) was mixed with aqueous hydrogen peroxide (50% w/w) (22 mol) at 40°C and adjusted to a pH of 2.0 - 2.5 with phosphate salts. Of this solution, 1.5 g of active bleaching solution was applied on same type and size of two different denim fabrics dyed with indigo (Denim 1 ) and sulphur black (Denim 2), then, kept in tumbler at 80 °C for 10 min. After that, the samples were rinsed with cold water without neutralization, followed by drying in a tumbler. The change in color strength is 50% for Denim 1 , 58% for Denim 2.

Example 4

Glutaric anhydride (1 mol) was mixed with aqueous hydrogen peroxide (50% w/w) (22 mol) at 40°C and adjusted to a pH of 2.0 - 2.5 with phosphate salts. Of this solution, 1.5 g of active bleaching solution was applied on same type and size of two different denim fabrics dyed with indigo (Denim 1 ) and sulphur black (Denim 2), then, kept in tumbler at 80 °C for 10 min. After that, the samples were rinsed with cold water without neutralization, followed by drying in a tumbler. The change in color strength is 45% for Denim 1 , 54% for Denim 2.

Example 5

Cyclohexane-1 ,2-dicarboxylic anhydride (1 mol) was mixed with aqueous hydrogen peroxide (50% w/w) (22 mol) at 40°C and adjusted to a pH of 2.0 - 2.5 with phosphate salts. Of this solution, 1.5 g of active bleaching solution was applied on same type and size of two different denim fabrics dyed with indigo (Denim 1 ) and sulphur black (Denim 2), then, kept in tumbler at 80 °C for 10 min. After that, the samples were rinsed with cold water without neutralization, followed by drying in a tumbler. The change in color strength is 60% for Denim 1 , 68% for Denim 2.

The invention, which is described in detail above, is a bleaching composition for oxidation and/or bleaching of the dyed textile products and basically comprising at least one cyclic anhydride; a hydrogen peroxide aqueous solution which includes excess hydrogen peroxide in a manner to have at least 20 times greater equivalent molar ratio in comparison to the said cyclic anhydride; at least one phosphate based alkali salt, which increases the solubility of the said cyclic anhydride in the hydrogen peroxide aqueous solution and adjust the pH of the acidic solution.

The invention discloses a bleaching composition maintaining active content of in situ prepared solution up to 48 hours, thanks to the conversion of the carboxylic acids, which are generated by decomposition of active bleaching ingredient peroxycarboxylic acids those generated by reaction of cyclic anhydride with hydrogen peroxide; to the peroxycarboxylic acids in presence of excess hydrogen peroxide.

In addition to these; the invention also discloses a method of oxidation and/or bleaching of dyed textile products; comprising treatment of the textile product with in situ prepared active solution without requiring a neutralization after treatment, wherein the solution is prepared in acidic pH conditions with at least one cyclic anhydride and a hydrogen peroxide aqueous solution which includes excess hydrogen peroxide in a manner to have at least 20 times greater equivalent molar ratio in comparison to the said cyclic anhydride and at least one phosphate based alkali salt. Here, the in situ prepared active solution maintains its active content up to 48 hours. Again, here, bleaching the said textile products, by using local spraying, fog or other methods can be performed in order to obtain local or effect bleaching. The applications can be performed at medium temperatures between 20 to 80°C. By the virtue of the said method; the indigo dyed light colored denim garments or sulphur dyed dark colored denim garments are bleached by treatment of the active solution at room temperature.

The ‘cyclic anhydride’ term that is mentioned in the present invention means an anhydride derivative of a carboxylic acid in a cyclic structure. Preferred embodiment of present invention comprising at least one cyclic anhydride selected from group of phthalic anhydride, glutaric anhydride, maleic anhydride, succinic anhydride, cyclohexane-1 ,2-dicarboxylic anhydride, pyromellitic dianhydride, ethylenediaminetetraacetic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-Oxydiphthalic anhydride and benzophenone-3,3',4,4'-tetracarboxylic dianhydride.

Preferred embodiment of present invention comprising at least one phosphate based alkali salt selected from the group of disodium hydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen, sodium tripolyphosphate, potassium tripolyphosphate, trisodium phosphate, tripotassium phosphate.

The pH of the active solution mentioned in the present invention is between pH 1 to pH 6; and it is preferably between pH 1.5 to pH 4.0.

The dyed textile products mentioned in the present invention comprise yarns, fabrics, and garments dyed with oxidizable dyes, indigo dyes, sulphur dyes or combination thereof.